Black Box Explains...Category 3 and 4
Category 3 is the performance level for voice and data transmission up to 16 MHz or 10 Mbps, such as 4-Mbps Token Ring and 10BASE-T.
Category 4 is the... more/see it nowperformance level for voice and data transmission up to 20 MHz or 16 Mbps, such as 4-/16-Mbps UTP.
Both offer solid performance, and Black Box guarantees their reliability. But if you think you may be upgrading your network within the next few years, consider Category 5 cable. It offers more speed and versatility than Category 3 or 4 at a minimal cost difference. collapse
Black Box Explains... KVM IP gateways
Just as a gate serves as an entry or exit point to a property, a gateway serves the same purpose in the networking world. It’s the device that acts as... more/see it nowa network entrance or go-between for two or more networks.
There are different types of gateways, depending on the network.
An application gateway converts data or commands from one format to another. A VoIP gateway converts analog voice calls into VoIP packets. An IP gateway is like a media gateway, translating data from one telecommunications device to another.
Gateways often include other features and devices, such as protocol converters, routers, firewalls, encryption, voice compression, etc. Although a gateway is an essential feature of most routers, other devices, such as a PC or server, can also function as a gateway.
A KVMoIP switch contains an IP gateway, which is the pathway the KVM signals use to travel from the IP network to an existing non-IP KVM switch. It converts and directs the KVM signals, giving a user access to and control of an existing non-IP KVM switch over the Internet. collapse
Black Box Explains...Selecting fiber line drivers.
When choosing a fiber driver, you should make a power budget, calculate the speed and distance of your cable run, and know the interface requirements of all your devices.
Many of... more/see it nowour fiber drivers are for single-mode fiber optic cable. Compared to multimode fiber, single-mode delivers up to 50 times more distance. And single-mode at full-duplex enables up to two times the data throughput of multimode fiber. collapse
Black Box Explains... PCI buses
A Peripheral Component Interconnect (PCI) Bus enhances both speed and throughput. A PCI Local Bus is a high-performance bus that provides a processor-independent data path between the CPU and high-speed... more/see it nowperipherals. PCI is a robust interconnect interface designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, SCSI, and LANs. collapse
Black Box Explains... Baseband, broadband, and carrierband transmissions.
Depending on the environment and how the electrical signal is sent over the cable, coax can be used for three types of transmissions.
Baseband transmissions use the entire communication channel capacity... more/see it nowto transmit a single data signal. Many LANs employ Thin coax for baseband signaling.
Broadband transmissions use different frequencies to carry several analog signals simultaneously. Each signal can for be a different type of information—data, voice, even video. Broadband transmissions over coax employ either one or two cables. With single-cable coax wiring, frequencies are split into individual channels for each station; some channels are allocated for bidirectional communication. Dual-cable coax wiring uses one cable for sending and one cable for receiving data, each with multiple channels. Broadband transmissions are ideal for long distances. Thick coax is often used for broadband transmissions.
Unlike broadband transmissions, carrierband transmissions can only use one information channel. Carrierband is best suited for the horizontal subsystems (subnetworks) in industrial settings. Many LANs use Thin coax for carrierband signaling. collapse
Black Box Explains...LAN switches.
Rush hour-all day, every day.
Applications such as document imaging, video/multimedia production, and intranetworking are very demanding. They generate huge data files that often must be transferred... more/see it nowbetween stations based on strict timing requirements. If such traffic is not transmitted efficiently, you end up with jerky video, on-screen graphics that take forever to load, or other irritating, debilitating problems.
These problems arise because in traditional LANs, only one network node transmits data at a time while all other stations listen. This works in conventional, server-based LANs where multiple workstations share files or applications housed on a central server. But if a network has several servers, or if it supports high-bandwidth, peer-to-peer applications such as videoconferencing, the one-station-at-a-time model just doesn’t work.
Ideally, each LAN workstation should be configured with its own dedicated LAN cable segment. But that’s neither practical nor affordable. A far more reasonable solution is a network designed to provide clear paths from each workstation to its destination on demand, whether that destination is another workstation or server.
These vehicles clear the lanes.
Unlike bridges and routers, which process data packets on an individual, first-come, first-served basis, switches maintain multiple, simultaneous data conversions among attached LAN segments.
From the perspective of an end-user workstation, a switched circuit appears to be a dedicated connection-a direct, full-speed LAN link to an attached server or other remote LAN node. Although this technique is somewhat different from what a LAN bridge or router does, switching hubs are based on similar technologies.
Which route will you choose?
Switching hubs that use bridging technologies are called Layer 2 switches-a reference to Layer 2 or the Data-Link Layer of the OSI Model. These switches operate using the MAC addresses in Layer 2 and are transparent to network protocols. Switches that use routing technologies are known as Layer 3 switches, referring to Layer 3—the Network Layer—of the OSI Model. These switches, like routers, represent the next higher level of intelligence in the hardware hierarchy. Rather than passing packets based on MAC addresses, these switches look into the data structure and route it based on the network addresses found in Layer 3. They are also dependent on the network protocol.
Layer 2 switches connect different parts of the same network as determined by the network number contained with the data packet. Layer 3 switches connect LANs or LAN segments with different network numbers.
If you’re subdividing an existing LAN, obviously you’re dealing with only one network and one network number, so you can install a Layer 2 switch wherever it will segment network traffic the best, and you don’t have to reconfigure the LAN. However, if you use a Layer 3 switch, you’ll have to reconfigure the segments to ensure that each has a different network number.
Similarly, if you’re connecting existing networks, you have to examine the currently configured network numbers before adding a switch. If the network numbers are the same, you need to use a Layer 2 switch. If they’re different, you must use a Layer 3 switch.
When dealing with multiple existing networks, you’ll find they usually use different network numbers. In this case, it’s preferable to use a Layer 3 switch (or possibly even a full-featured router) to avoid reconfiguring the network.
But what if you’re designing a network from scratch and can choose either type of switch? Your decision should be based on the expected complexity of your LAN. Layer 3 routing technology is well suited for complex networks. Layer 2 switches are recommended for smaller, less complex networks. collapse
Black Box Explains...On-screen menus.
When the ServSwitch™ brand of KVM switches was first introduced, there were only two ways to switch: from front-panel push buttons or by sending command sequences from the keyboard. While... more/see it nowthis was more convenient than having a separate keyboard, monitor, and mouse for each CPU, the operator still had to remember key combinations and which server was connected to which port—leading to many cryptic, scribbled notes attached to the switch and to the workstation.
But with the advent of on-screen menus, an operator can use easy-to-read, pop-up menus to identify and select CPUs. It’s even possible to give each CPU a name that makes sense to you—names like “MIS Server,” “Accounting Server,” and so on.
Black Box Explains…Component vs. channel testing.
When using a Category 6 system, the full specification includes the testing of each part individually and in an end-to-end-channel. Because CAT6 is an open standard, products from different vendors... more/see it nowshould work together.
Channel testing includes patch cable, bulk cable, jacks, patch panels, etc. These tests cover a number of measurements, including: attenuation, NEXT, PS-NEXT, EL-FEXT, ACR, PS-ACR, EL-FEXT, PS-ELFEXT, and Return Loss. Products that are tested together should work together as specified. In theory, products from all manufacturers are interchangeable. But, if products from different manufacturers are inserted in a channel, end-to-end CAT6 performance may be compromised.
Component testing, on the other hand, is much stricter even though only two characteristics are measured: crosstalk and return loss. Although all CAT6 products should be interchangeable, products labeled as component are guaranteed to perform
to a CAT6 level in a channel with products from different manufacturers.
For more information on cable, channel, and component specs, see below.
Buyer’s Guide: CAT5e vs. CAT6 Cable
Standard — CAT5e: TIA-568-B.2; CAT6: TIA-568-B.2-1
Frequency — CAT5e: 100 MHz; CAT6: 250 MHz
Attenuation (maximum at 100 MHz) —
Cable: CAT5e: 22 dB; CAT6: 19.8 dB
Connector: CAT5e: 0.4 dB; CAT6: 0.2 dB
Channel: CAT5e: 24.0 dB; CAT6: 21.3 dB
NEXT (minimum at 100 MHz) —
Cable: CAT5e: 35.3 dB; CAT6: 44.3 dB
Connector: CAT5e: 43.0 dB; CAT6: 54.0 dB
Channel: CAT5e: 30.1 dB; CAT6: 39.9 dB
PS-NEXT (minimum at 100 MHz) — 32.3 dB 42.3 dB
EL-FEXT (minimum at 100 MHz) —
Cable: CAT5e: 23.8 dB; CAT6: 27.8 dB
Connector: CAT5e: 35.1 dB; CAT6: 43.1 dB
Channel: CAT5e: 17.4 dB; CAT6: 23.3 dB
PS-ELFEXT (minimum at 100 MHz) — CAT5e: 20.8 dB; CAT6: 24.8 dB
Return Loss (minimum at 100 MHz) —
Cable: CAT5e: 20.1 dB; CAT6: 20.1 dB
Connector: CAT5e: 20.0 dB: CAT6: 24.0 dB
Channel: CAT5e: 10.0 dB; CAT6: 12.0 dB
Characteristic Impedance — Both: 100 ohms ± 15%
Delay Skew (maximum per 100 m) — Both: 45 ns
NOTE: In Attenuation testing, the lower the number, the better. In NEXT, EL-FEXT, and Return Loss testing, the higher the number, the better.
Black Box Explains... Matrix video switches.
Matrix switches enable computers to mix and match the output of multiple PCs on multiple video monitors.
For instance, if your operation has four PCs and you want to display the... more/see it nowvideo on one monitor to the other three monitors, a matrix video switch is what you need to handle the job. Use matrix switches for:
• Trade showsSet up a wall of video to wow the senses of attendees.
• Transportation schedulesProvide real-time updates of flights or deliveries on multiple screens.
• Training demonstrationsControl each screens video to focus everyones attention on whats important. collapse
Black Box Explains...Layer 3 switching.
In the last decade, network topologies have typically featured routers along with hubs or switches. The hub or switch acts as a central wiring point for LAN segments while the... more/see it nowrouter takes care of higher-level functions such as protocol translation, traffic between LAN segments, and wide-area access.
Layer 3 switching, which combines Layer 2 switching and Layer 3 IP routing, provides a more cost-effective way of setting up LANs by incorporating switching and routing into one device. While a traditional Layer 2 switch simply sends data along without examining it, a Layer 3 switch incorporates some features of a router in that it examines data packets before sending them on their way. The integration of switching and routing in a Layer 3 switch takes advantage of the speed of a switch and the intelligence of a router in one economical package.
There are two basic types of Layer 3 switching: packet-by-packet Layer 3 (PPL3) and cut-through Layer 3.
PPL3 switches are technically routers in that they examine all packets before forwarding them to their destinations. They achieve top speed by running protocols such as OSPF (Open Shortest Path First) and by using cache routing tables. Because these switches understand and take advantage of network topology, they can blow the doors off traditional routers with speeds of more than 7,000,000 (thats seven million!) packets per second.
Cut-through Layer 3 switching relies on a shortcut for top speed. Cut-through Layer 3 switches, rather than examining every packet, examine only the first in a series to determine its destination. Once the destination is known, the data flow is switched at Layer 2 to achieve high speeds. collapse